This invention relates to an apparatus and method for a ventilator system and more particularly to such an apparatus and method for a high frequency ventilator system for delivering gas to the airway of a patient.
Heretofore, ventilators have produced gas exchange with the lungs with a frequency generally around the natural frequency of a normal patient's breathing. Such ventilators or ventilator systems have used mixtures of air and oxygen which are humidified and warmed to body temperature and then forced into the lungs under a positive pressure which is adequate treatment for the majority of patients requiring assisted respiration. When patients are exposed to pressure breathing for long time periods however, complications can occur that become life-threatening. Sometimes physiological situations develop that cause the mechanical ventilator to be operated at its maximum limits, and the patient will continue to decline possibly resulting in death. Such situations may occur, for example, from a collapse of the lungs, from the lungs becoming filled with secretions, from airway obstructions, from lungs losing their elasticity, and the like. In these situations, ventilators heretofore have been generally ineffective, particularly in meeting the requirements for such a wide range of complications.
Heretofore, such as shown in U.S. Pat. No. 4,481,944, dated Nov. 13, 1984, a method and apparatus have been provided in a system for applying high frequency positive pressure pulses of gas to an airway of a patient to assist breathing and ventilation. An inhale valve for such gas pulses is opened and closed in response to signals received from a microprocessor. Signals from a temperature sensor and a pressure sensor indicating the temperature and pressure of the gas supplied to the patient are provided to the microprocessor which then supplies appropriate signals to a heater and drive means for controlling the temperature and pressure of the gas supplied to the patient. Additionally, as shown in aforesaid U.S. Pat. No. 4,481,944, the frequency of the gas frequencies, such as from two (2) to thirty (30) hertz or cycles per second. However, the range of frequencies included the natural frequency of the patient's respiratory system at least part of the time and ranged generally between five (5) and ten (10) hertz below the natural frequency, and five (5) to ten (10) hertz above the natural frequency.
Improvements in conventional ventilators have been provided such as illustrated in U.S. Pat. No. 4,036,221, dated July 19, 1977; U.S. Pat. No. 4,527,557, dated July 9, 1985; and U.S. Pat. No. 4,587,967, dated May 13, 1986 which utilize microprocessors receiving input signals from various sensing devices and then sending output signals for controlling the operation of the ventilator. However, such ventilator devices, some of which provide high frequency gas pulses, have not been effective in meeting requirements for a wide range of lung complications encountered as well as assisting normal respiration even though the mechanical breathing action of such ventilators is substantially improved.
Such conventional and high frequency jet ventilators push or force a relatively large volume of air into the lungs in a relatively short period of time, such as one thousand (1,000) cubic centimeters per second and thus, a substantial portion of the air is compressed within the airway or bronchus without reaching the functional areas of the lungs.